That milk in the back of your fridge. That check your bank is no longer willing to cash.
And you. What do all these things have in common?
They all have an expiration date.
Ben Franklin said there are only two things certain in life - death, and taxes. However,
certain prominent citizens have proven it’s a lot easier to get out of paying taxes than it
is to live forever. From the moment we’re born, we’re all ticking down towards the finish line.
It seems to be the one immutable rule of life. From that plant that never seemed
to flower no matter how much sun you gave it, to your beloved first goldfish Floaty,
to the most powerful King or President, every single living being on Earth will inevitably die.
But why? Why were we all born to eventually expire?
What purpose does this serve in evolution to give us all a limited time on this planet?
It’s far from exclusive to humans - we’ve had the opportunity to study the life cycles of
most animals and plants and those that don’t die of other causes will inevitably die of old age.
Life cycles vary, but all follow a similar pattern of growth, peak years, and natural decline as
they get older. What is unique to humans is an awareness of our own mortality, and the desire
to understand what comes before, during, and after death. End-of-life care, the branch of
medicine dedicated to making people comfortable in their last year, makes up roughly ten percent
of overall medical spending, encompassing those who die from both illnesses and from old age.
But it wasn’t always this way.
Hundreds of years ago, old age was a much rarer way to go out. Life expectancy was dramatically
shorter, and people were more likely to die from injury, contagious disease, infection,
or malnutrition. Many of these causes still persist in countries and regions around the world,
but the advance of medical treatment and the industrialization of food production
has cut them down and let other causes take the lead. The leading causes of death now
include heart disease, stroke, respiratory infections, dementia, cancer, and diabetes. These
non-contagious illnesses can affect people of any age but become more likely the older people get.
And of course, there’s one common cause of death - old age, right? Wrong!
Would it surprise you to know that no one has ever died of old age? Age isn’t a cause of death,
it’s a risk factor that eventually leads people to succumb to an ailment associated with aging.
The government mandates that every death certificate lists the cause of death,
so when someone dies suddenly or in their sleep without an obvious cause of death, it used to be
frequently listed as “natural causes” or “old age”. This is starting to change. Every one of
these cases has an underlying cause and as medical science presses forward, coroners are becoming
more skilled at pinpointing the cause of death. The exception may be when someone dies peacefully
at home after a long life, and their family doesn’t want an autopsy or investigation. Also,
a very old person who has been beating the odds for a long time may have a lot of underlying
ailments and it can be hard to determine which was the one that led to their death.
So does the human body have a natural expiration date?
It’s rare for a person to live past a hundred years old, although this group - centenarians - is
the fastest-growing population demographic in industrialized nations due to the advances in
medical care. There’s an even rarer group, super-centenarians, who have lived to
a hundred and ten and beyond! The verified oldest person ever to live, Jeanne Calment,
was a French woman born in 1875 who died in 1997, although questions about her story have
emerged in recent years - with some claiming her daughter was impersonating her in her last years.
Most experts still credit her as being the only person to ever live past a hundred and twenty,
outliving runner-up American Sarah Knauss by over three years. They should both watch out,
though, because the person in third place is still kicking. Kane Tanaka of Japan is
currently about to turn a hundred and eighteen on the second day of 2021.
So is there a secret to living this long,
or did Jeanne, Sarah, and Kane find the fountain of youth?
Those who live to over a hundred tend to have similar characteristics, such as eating well;
exercising regularly, avoiding smoking and stress, being connected to family,
and having an overall good attitude towards life. The average centenarian is also shorter
and lighter than the average. But other factors like location and environment play a role too.
Unusual concentrations of centenarians have been found in places as far apart as Okinawa,
Bulgaria, and Sardinia. Okinawa has the highest concentration of centenarians,
with five hundred per million residents, and scientists give a lot of the credit to
their diet and comparably low caloric intake, which may reduce wear and tear on the body.
Is it possible to learn from this and extend the human lifespan further?
Research into the nature of death has led to experiments in areas like cryonics, where beings
are preserved immediately after death for possible treatment and resurrection in the future. However,
this is all theoretical at the moment, as no being has ever been resurrected after death and cryonic
freezing in tests. Techniques like reperfusion, where oxygen is pumped into the blood in a very
controlled manner to prevent cell death, have been used to test the theory but may have more
use in standard medical treatment rather than in reversing death for now. Other concepts,
like developing digital uploads of the brain and transferring them into a clone body, remain
firmly in the realm of science-fiction for now. At least at this point in time, everything dies.
But what purpose does this serve in evolution? Why have millions of years
of development never managed to outgrow death?
There are many theories for the purpose death plays in evolution, and several have
been debunked. A common early theory was that we die so that younger generations can replace us.
This doesn’t make sense with the primary purpose of life, though - we’re a collection of genes,
and the death of an older person makes room for only one more person by their absence. As genes
only have a fifty-percent chance of being passed on to the next generation through the parent,
it doesn’t make sense for evolution to develop death to favor the offspring over the parent.
There’s also the theory that we die because our cells or DNA naturally degrade with age.
That’s true, but it’s an effect, not a cause. Our cells mutate as they divide,
and the more cells divide the higher the chance of a mutation. This can cause medical problems,
but our cells are constantly reproducing and can usually overwhelm any mutated cells. The
exception? Cancer cells, which reproduce and overwhelm the healthy cells. Cells only have
a certain number of divisions before they reach the end of their natural lifespan.
Observations of other species indicate that lifespan varies dramatically between species
and species with a higher risk of death from other means are likely
to have a shorter life expectancy. We’re toward the higher end of the spectrum.
So why hasn’t evolution taken care of this pesky death thing yet,
or at least kept stretching it out, if it can affect life expectancy so dramatically?
The problem is, evolution isn’t here to be our friend. The priority is the long-term health
and survival of the species, not any individual, and that means genes are more likely to evolve
to focus on reproduction than preservation. Any individual can be cut down by anything at any time
- a sudden heart attack, a fall down the stairs, or a piano falling on your head from the tenth
floor. That randomness of life and the chance of a sudden death means that over a long process
of evolution, the gene mutations that are likely to further the long-term survival of the species
are the ones that will remain, and those that don’t further this goal will naturally die out.
At least every living being on the planet is in the same boat, right? Yes and no.
If you want to live forever, your best bet is to be a tree. When undisturbed,
these towering plants grow and grow, only to be felled by human intervention or natural disaster.
Several trees around the world are confirmed to be well over a thousand years old,
with the oldest known tree being a bristlecone pine from California’s White Mountains,
clocking in at a staggering five thousand and sixty-seven years old from a sample of its core.
That means this specific tree was standing before the Great Pyramid of Egypt was built.
But what about animals? Have any of them managed to beat the strictures of mortality?
Life expectancy among animals varies dramatically, with some insects only having a lifespan of days
or weeks. It’s common for small mammals to only live a few years, as many a kid whose parents
replaced their beloved hamster Snowball with an identical one while they were at school found
out. Even powerful apex predators like the bear or tiger only live ten to twenty years in the wild.
Some of our closest relatives, like the gorilla or chimpanzee, can live closer to a human lifespan
but top out at around thirty-five to forty years - barely middle age for a human. So we can feel
pretty good about our average lifespan of the seventies and beyond. We’re beating the odds!
There are a few animals, though,
who have managed lifespans that would make the average human jealous.
The animals that can live well into their hundreds are diverse, and some are unexpected.
Everyone remembers flushing their pet goldfish down the toilet after an unexpectedly short stay,
but one of their close relatives, the Koi fish, live up to thirty years on average. However,
one famous Koi named Hanako was found to be over two hundred years old based on the growth
rings on her scales! Koi aren’t the only sea creatures that can live longer than most humans,
with Longfin Eels living up to 106 years old and sea urchins living into the two hundred range.
Bowhead whales have an average lifespan of two hundred years,
with one being found with a fragment of a harpoon in its skin dating back to the 1800s. The likely
champ of long lives in the ocean, though, is the Greenland Shark. Located in the arctic circle,
this shark grows very slowly and doesn’t even reach maturity until they’re a hundred years old.
The oldest living specimen? Four hundred years old, putting it in a range only trees can reach.
But what about land animals? Can they compete with the aging kings of the seas?
There are a lot of land animals that can live close to human lifespans,
including elephants that live up to seventy years. That’s a lot of time to never forget anyone. And
if you can’t bear saying goodbye to another pet who will die after two to fifteen years,
consider getting a parrot. There’s a good chance the colorful bird will outlive you
with a lifespan of fifty years or more. But the longest-living land animal is one that proves
the value of taking it slow. The Galapagos Giant Tortoise, native to the remote islands, can live
well past one hundred. Their most famous specimen, Lonesome George, lived to a hundred and one, but
specimens have been reported to make it past the one hundred and fifty-year mark. However,
the tortoise couldn’t outlast extinction, as sadly Lonesome George was the last of his kind.
This just proves that no matter how long we or any species live,
there’s a ticking clock. Death comes for every living thing - right?
It turns out there are a few species that may have come closer to beating death than
any other. These are species that avoid the typical process of senescence, the gradual
deterioration of cell function. Lobsters are able to constantly repair their own DNA,
shedding their own shells through a difficult process while the inner tissue stays healthy
thanks to an endless supply of an enzyme that repairs their telomeres. The problem that keeps
them from being truly immortal is that they get too big for their shells, and it eventually takes
too much effort to shed the old shell, and the lobster succumbs to diseases.
Of course, for many lobsters, the end comes much quicker than that, courtesy of a fisherman’s trap.
Meanwhile, a jellyfish species named Turritopsis Dohrnii stunned scientists
when it seemingly unlocked the key to immortality. These tiny,
translucent animals are found in oceans around the world and have a unique method
for preventing death. They literally turn back the clock by turning back into a tiny blob
that starts the life cycle anew. Imagine if instead of dying when we hit old age,
we just turned back into a baby again. While these jellyfish can easily die for good when
they’re consumed by a predator, their natural life cycle doesn’t seem to have a traditional end.
This raises the question, though, of what death truly is. These jellyfish may continue their life
cycle by restarting it, but this would likely be impossible for a more complex form of life
that thinks and learns. Still, scientists are avidly studying these strange creatures
to see if they can unlock more of the mystery surrounding our life cycle. Even as we study
death across the living kingdom it remains, for almost everything on Earth, inevitable.
For more on what happens to us when we die, check out “What Happens When You Die?”,
and for a very modern part of death, why not watch “What Happens to Your Online Life When You Die?”